#include <stdio.h>

int main(void)
{
	int n,an,x,i,a;
	double v;
	scanf ("%d,%d,%D",&n,&an,&x);
	v=a;
	i=n-1;
	while(i >= 0)
	{
		scanf("%d",&a);
		v=v*x+a;
		i--;
	}		
	printf("v= %lf",v);
	return 0;
}